Cooling systems are used for cooling purposes in different applications, such as e.g. for cooling radio transceiver units in telecom equipment, etc.
A component to be cooled such as a PCB or a power amplifier may be cooled using a heat sink by placing the component to be cooled against the heat sink base in order to be able to transfer heat from the component to the heat sink.
If more cooling power is needed, it is possible to arrange forced cooling of the heat sink, i.e. to arrange a fan that forces a flow of air across the surfaces of the heat sink cooling fins thereby replacing the air around the cooling fins which air has been heated by the heat from the cooling fins with cooler ambient air from the outside of the heat sink.
Normally, radio units, e.g. radio transceivers, are installed on top of a tower or at a similar high mounting position. As the efficiency of e.g. power amplifiers in radio units is not 100%, they emit heat, i.e. the radio unit comprises heat generating components whereby the radio unit needs to be cooled. As mentioned above, one possibility is to cool the radio unit by using traditional air cooled heat sinks with fans for forced convection cooling or without fans for so called natural convection cooling.
Due to the often limited base area of a heat generating component in a radio unit and the desire to place more and more functionality on a defined base area of a component, more powerful components are developed. This increase in component capacity may e.g. be accomplished by building higher integration components. This increase in component capacity leads to that more power may be fed to components per component base area than before which in turn results in that the components emit more heat per base area than before when in maximum use e.g. during peak traffic in telecom systems, i.e. the maximum heat load of components is increasing as they may be fed with more power per square centimetre (W/cm2) base area. This is also the case for e.g. power amplifiers in radio units. Need of increased performance from radio units means increased heat dissipation, which in turn means need of increased cooling performance. For radio units with heat sinks for natural convection cooling there is increasing difficulties as these have to be of such dimensions that their size and weight results in the need for stronger mountings and reinforcement of e.g. towers and very large sizes that are not accepted on the market. Radio units may be cooled with forced convection with some apparatus, which can force air through a heat sink, e.g. by using fans.
When forced cooling with air of a heat sink placed with its base against the component, such as an power amplifier in a radio unit in a tower, to be cooled is insufficient or requires heat sinks of very large dimensions to cool the components, other methods may be used such as liquid cooling.
U.S. Pat. No. 6,094,929 shows remote cooling of radio transceivers, e.g. by using liquid cooling.
U.S. Pat. No. 7,355,852 B2 shows modular liquid cooling of electronic assemblies.